Such a deflection system, also called a deflector or deflection yoke assembly generally comprises of a pair of vertical deflection coils, a pair of horizontal deflection coils, and a ring essentially in the shape of a truncated cone of magnetic material intended to concentrate the flux created by the coils. The horizontal deflection coils are generally in the shape of a saddle; the vertical deflection coils may also be saddle shaped, or may be formed as a torus wound around a ring of magnetic material.
The two pairs of deflection coils are insulated electrically by a separator, generally of plastic material. In addition the separator provides mechanical rigidity to the deflection device, allows positioning of the coils relative to each other and facilitates adjustment the assembled unit on the tube neck. The separator comprises a main body, and one or more parts, essentially in the shape of a funnel, with a flexible back part which adjoins the neck of the tube to allow the deflection system to secured on the longitudinal or Z axis of the tube. This tube neck attachment is generally accomplished by a collar or clamp arranged about the flexible back part of the separator.
During the assembly of the components comprising the deflector, the deflection coils are installed on the separator and positioned one with the other to enable the generation of vertical and horizontal deflection fields, in accordance with the cathode ray tube with which the deflector is intended to operate. The deflector is then located on the tube neck and positioned along the axis Z of the tube such that in the absence of deflecting fields, the three electron beams generated by the electron gun converge at the CRT screen. The deflector is maintained in this position generally by means of the locking collar or clamp positioned on the back annular part of the separator. The annular part of the separator is designed to have the necessary flexibility to facilitate the sliding introduction of the deflector onto the tube neck and the subsequent locking thereon.
However, this yoke assembly clamping method requires that the outer annular surface of the separator, at the back end of the deflection coils, extends beyond the coils to provide the necessary flexible area for clamping following Z axis adjustment. Thus the length of the yoke assembly may influence the other neck components and the length of the tube neck which supports them. The tube neck and yoke assembly lengths are of particular importance with deflectors having saddle shaped vertical deflection coils which extend further along the Z axis than toroidally wound coils. In addition, since the trend in current television receiver design is directed to a reduction in overall size and, since the overall dimensions are largely determined by the cathode ray tube, receiver depth may be reduced by the use of CRTs with shorter neck lengths thus requiring yoke assemblies with a similar length reduction.